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The Oral Microbiome

As we work to heal the gut microbiome and reduced intestinal permeability, we also must consider the oral microbiome. This pivotal factor is often overlooked in autoimmune conditions (and other chronic diseases), even though it has powerful effects on dental health and diseases, the gut microbiome, and systemic inflammation.

Through multiple mechanisms, oral bacteria can play a role in disparate conditions like cardiovascular disease, diabetes, colon cancer, lung infections, brain abscesses, and autoimmunity.i For this reason, the oral microbiome has a substantial impact on the immune system and can sometimes be the missing link in terms of helping a patient with autoimmunity to achieve remission.

The oral microbiome contains the second largest collection of bacteria in the body after the gut, harboring around 6 billion bacteria and over 700 different species.ii Although this microbiome is relatively well-studied, newer more advanced techniques have found that these numbers are likely underestimating the quantity and diversity of bacteria.

We swallow a whopping 1-2 L of saliva per day. Assuming on the low end that we swallow only 1 L per day leads to an interesting calculation. Considering that saliva contains between 800 million to more than 1 billion bacteria/mL,iii that works out to an incredible 800 billion to > 1 trillion oral bacteria swallowed per day – more powerful than almost any probiotic available on the market. And there are no breaks or “days off” from this influx of bacteria – it is a constant and daily occurrence. From this, we can understand how the oral microbiome could have such a significant impact on the gut microbiome and overall systemic inflammation.

A Key Player in Autoimmunity

Porphyromonas gingivalis (P. gingivalis) is an oral bacterium that is involved in the pathogenesis of periodontitis, an inflammatory disease that destroys the gums and can lead to tooth loss. It also plays a key role in rheumatoid arthritis, as these bacteria are potent inducers of immune mediated proinflammatory responses leading to bone damage and systemic inflammation.iv P. Gingivalis is also implicated in rheumatoid arthritis through molecules known as “citrullinated proteins”

Accumulating evidence suggests a role for autoimmunity against these citrullinated proteins in the development of rheumatoid arthritis. By driving the production of these proteins, this bacteria may contribute to the development of RA. In fact, anti-cyclic citrullinated protein antibodies (anti-CCP antibodies) are the most common rheumatoid arthritis biomarker, found in the blood of most patients with RA. A more recently discovered bacteria, Aggregatibacter actinomycetemcomitans, is also an inducer of citrullinated proteins and is being studied for its role in RA.v

Leaky Mouth Syndrome

The epithelial cells lining the mouth maintain a strong barrier, limiting the entry of microbes and toxins, because the mouth is the gateway to the world and the first line of defense against pathogens. Just as dysbiosis in the G.I. tract contributes to impaired barrier function, oral dysbiosis can lead to increased permeability and the condition of “leaky mouth,” in which inflammation in the oral mucosa caused by dysbiosis and other factors damages the normal barrier, allowing for the entry of bacteria, toxins, and other microbes into the bloodstream.

Because the mouth and gums are highly vascular, anything that slips through can easily travel to other parts of the body and cause complications—as with P. gingivalis. A striking example of this permeability was seen in a 9-year-old with celiac disease (an autoimmune disease exacerbated by gluten exposure) who struggled with abdominal pain despite a strict gluten-free diet. She was symptomatic and had positive serum markers for active disease, which indicated she was somehow getting exposed to gluten. The cause for this turned out to be her orthodontic retainer—gluten is a common additive in plastics, and she was absorbing trace amounts orally. Discontinuing use led to resolution of her symptoms and her celiac markers returned to

From The TIGER Protocol: An Integrative, 5-Step Program to Treat and Heal Your Autoimmunity, by Akil Palanisamy, MD published by Balance. Copyright © 2023 by Akil Palanisamy, MD.

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